ECM Equipment

Figure 2 shows a schematic representation of the ECM system for finishing of a die or other complex shapes. The major components include the workpiece, cathode tool, electrolyte, power supply, and electrolyte circulating and purification system. A low voltage (8 to 30 V) is normally applied across the electrodes. A small gap (0.2 to 1 mm) is maintained between them, producing a current density of the order of 10 to 100 A/cm2 (Ref 1, 2, 3). The electrolyte is forced through the small gap between the cathode tool and the anodic workpiece with velocities of 5 to 30 m/s (15 to 100 ft/s). The electrolyte movement flushes away the debris removed from the workpiece.

Fig. 2 Electrochemical machining equipment schematic. 1, tool electrode; 2, finishing workpiece; 3, tank of electrolyte; 4, clamping system; 5, electrolyte supply system; 6, power supply

A typical ECM machine consists of a table for mounting the workpiece and a platen mounted on a ram or quill for mounting the tool. The workpiece is mounted on the table and connected to the positive side of the power supply. The tool is mounted on the platen with electrical connection to the negative side of the power supply. The part to be machined is held on a fixed table and the tool is held on a ram that moves either horizontally or vertically onto the workpiece. During the finishing operations while ECM sinking, the tool is either stationary or is fed in the direction of the workpiece. During deburring and machining of contours, however, the tool usually does not move relative to the workpiece.

The corrosive nature of the electrolyte requires that any portion of the machine or tooling that comes in contact with it must be made of a corrosion-resistant material. Workholding fixtures for ECM are usually made from stainless steel, copper, or copper alloys.

Water-cooled power supplies are used on ECM equipment to convert alternating current (ac) electrical power to the direct current (dc) voltages required. ECM machines are available that can deliver currents from 50 to 10,000 amperes, with a voltage range of 4 to 30 V. Sufficient current must be available to maintain a current density of 10 to 500 A/cm2 at the workpiece (Ref 1, 3).

References cited in this section

1. G.E. Benedict, Nontraditional Manufacturing Processes, Marcel Dekker, 1987

2. J.A. McGeough, Principles of Electrochemical Machining, Chapman and Hall, London, 1974

3. C. Wick and R.F. Veilleux, Ed., Materials Finishing, and Coating, Vol 3, Tool and Manufacturing Engineers Handbook, Society of Manufacturing Engineers, 1985, p 15.24-16.126

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